Although chemical methods have been proposed to remove soluble organic matter (SOM) from hydroponic solutions, it may be a benefit to retain this material to improve nutrient solution mineral bioavailability. Like chelates, SOM can enhance bioavailability by complexing nutrient ions, and thus, preventing precipitate formation. Iron phosphate is a common precipitate that forms in hydroponic and soil solutions. Initial studies have shown that wheat (Triticum aestivum L. cv. Apogee) plants grown in solution culture containing 35 μM Fe supplied as either FeCl3 + HEDTA, or FeCl3 + HA (commercial humic acid) resulted in comparable growth and seed yields. Leaf tissue Fe content was similar between treatments but Zn concentrations were greater in leaves grown with HA until 42 days, after which there were no treatment differences. Ongoing studies will isolate and chemically characterize the SOM obtained from bioreactor effluents and examine their role in nutrient bioavailability.